Disable ICMP Redirect for security

If your running server versions, add the following reg_dword in the location shown and set it to "0". This will help keep an icmp re-direct attack from taking over your server.

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters]
"EnableICMPRedirect"=dword:00000000

Works in both Win2k and XP

Source: http://tweaks.com